Airborne geomagnetic mapping with an unmanned aerial vehicle

Abstract

In the last decade, technological advances in the field of multicopters enabled a widespread use of drones that include professional research applications covering a wide field from civil engineering to geosciences and agriculture. In recreational spheres drones became popular for sport and leisure activities like private photography. In geophysics, multicopters opened new doors for easier and cheaper airborne surveying especially with electromagnetic sensors such as geomagnetometers and georadar.
In this study we developed an airborne geomagnetic mapping system by combining commercially available components. Our setup consists of a DJI M600 drone with a SENSYS Magdrone R3 sensor mounted on the drone’s landing gear. First measurements showed that data processing requires correcting for the multicopter’s varying orientation during the flight, which impacts the magnetic recordings. The correction of this so-called heading error can be addressed using a scalar calibration scheme, which was originally developed for satellite missions. The calibration is performed by a specific maneuver in flight and compensates the vehicles magnetic influence on the magnetic recordings. We demonstrate how a high data quality can be achieved using a newly developed calibration algorithm for our drone-sensor-setup and how geomagnetic data can be processed in such a way that a reliable qualitative interpretation is achievable.
In a case study we conducted an airborne geomagnetic mission in Forel (FR, Switzerland) at a military bombing range near Payerne, which is used as a training facility for target practices. The study area consists of an inaccessible swamp and shallow water zone, where ammunition was documented to be shot and dumped throughout the last century. The results show that our setup allows to reliably locate magnetic anomalies as they are produced by dropped ammunition. Therefore, fast and safe geomagnetic surveying is possible, and it can aid in future not only for UXO detection but also for identifying abandoned landfills and geological structures.